Ummm, no... As it says in the first paragraph of the article:
"The discovery points to an internal heat source that, at some point in Pluto’s past, drove the melting of interior reservoirs of volatile ices, such as nitrogen and methane, that then erupted at the surface."
So, by "ices," they mean frozen N2 and CH4 - not frozen H2O, which would remain rock-solid at temperatures at which nitrogen and methane would have long since transformed into liquids or even gasses.
Regards,
Well, okay then.